


Across Time and Space

by eikuuhyo



Category: Undertale (Video Game)
Genre: Angst, Fluff, Fontcest, Hurt/Comfort, Incest, M/M, Voyeurism
Language: English
Status: In-Progress
Published: 2015-11-15
Updated: 2015-12-01
Packaged: 2018-05-01 19:59:41
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 5
Words: 4,241
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5218907
Author URL: https://archiveofourown.org/users/eikuuhyo/pseuds/eikuuhyo
Summary: <blockquote class="userstuff">
              <p>Sans has lived through reset after reset, forced to live through timelines before everything starts over again. He still wishes to save Gaster, who is scattered across the timelines, yet even that is seemingly impossible. Eventually, he begins yearning for comfort and there is only one he can think of...</p>
            </blockquote>





	1. Reset

**Author's Note:**

> I've been wanting to write some fontcest, and so I decided to start one where every chapter is a new timeline. Each chapter will be a short drabble to just get some fontcest ideas out of my head. There will be angst, hurt/comfort, fluff, and some skelesinning along the way.
> 
> All NSFW chapters will be labeled as such.

Another reset. Another timeline.

Sans awoke this time in the middle of the forest near Snowdin, the memories of the previous time hitting him like a ton of bricks. He cannot fight the sob that leaves his throat as he clutches himself. Tears fall from his eyes as he mutters out a small, "Why...?"

The timeline he had been in seemed like it was finally the end of the cycle. Frisk had succeeded in saving everyone, including Flowey, and the barrier was gone. He and his brother Papyrus had been happy, watching the sun set over the horizon. He had held Sans' smaller hand and was beaming with joy at the beautiful view. Even Frisk had joined in and held his other hand, vowing that things were finally over... That everyone, including Sans, would be able to live in freely.

But as soon as those words were said, Frisk suddenly disappeared with a look of shock on their face. Papyrus was next, the last thing Sans remember seeing is the look of panic on his brother's face as he disappeared. Asgore, Toriel, Undyne, the other monsters... They all vanished, along with the scenery, and Sans was falling into the void.

And here he was now, back underground. Sans knew that this reset was not done by Frisk, yet he couldn't help but wonder who else could've triggered it...? Was there some other being out there with the power to wipe everything that happens and watch as the world continues round and round?

It's hours before Sans finally wipes the tears and stands back up. If the timeline has truly been reset, then there are a few days before Frisk will come through the doors of the Ruins. He needs time to recollect himself, to be able to guide the child on the correct path... again. He had to be resolved. He had to do it, for the sake of the other monsters, for his brother Papyrus, and for his long lost friend and formerly lover... Gaster.

Perhaps that was why the rest occurred? Because he had not found a way to save Gaster? Such thoughts continued to plague his mind as Sans slowly trudged through the snow to their house. It was deep into the night and there isn't a soul out on the streets, to which he is quite thankful for. Sans didn't need anyone to see him like this.

When he finally unlocks the door to their house and slips inside, only then does he exhale a tired sigh. The walk through the frigid air has cleared his mind a little. Still... he can't stop himself from walking upstairs and quietly opening his brother's room to see if Papyrus is home. A quick peek in reveals that his brother is indeed fast asleep in his race car bed. The sight makes Sans smile, at least.

As hard as it is to see the world be turned around again, at least he has his brother. The reason why he can keep doing this. The only reason why he feels that he still exists.

"...Don't worry, bro," Sans whispers while lightly patting Papyrus' skull. "I can't give up... I won't until everyone—you—can live happily above ground."

Another, more gentle smile appears on Sans' face as Papyrus mumbles something about spaghetti and humans before rolling to his side. Sans gives him a small, mock kiss on his skull and then leaves his brother's room.

Tomorrow will be another day. Another day for him to try and find a way to save everyone. Another day, that he will force himself to smile, for Papyrus' sake.

"I can do this," Sans mutters to himself once more as he slips into his own bedroom and dives under the blankets. "I have to do this..."

And with that, the small skeleton fell into a deep slumber.


	2. Do You Need a Hand? (NSFW)

**Summary for the Chapter:**

> Everyone thinks that Papyrus is an innocent, child-like monster, but he's more knowledgeable about sexual things than other monsters think. In comes the obvious scenario of Sans accidentally walking in on him while he's pleasuring himself.

Today had been a good day for Sans. He had a nice knock-knock joke time with the lady beyond the doors at the Ruins, worked his post at the edge of the forest, sold some water sausage hot dogs... By the time he got home, he was ready to chat with his brother for a bit before hitting the hay.

He unlocks the front door to find that the house is pitch black. There is a strong smell of tomato sauce wafting downstairs, an obvious indication that Papyrus had made spaghetti for dinner. With a shrug, Sans shakes off the snow that is on his shoulders and then begins heading upstairs. Considering the faint sounds coming from Papyrus' room, he must be still up.

"Hey bro, I'm ho—" Sans says as he walks into the room, not even bothering to knock. He freezes dead in his track, mouth hanging slightly open at the sight laid before him.

Papyrus is sitting on his race car bed, eyes tightly closed with an orange blush on his bony cheeks and small "nyehs" falling from his mouth as his hand is tightly gripped around... what could only be described as an orange glowing, ghostly dick. Sans can't take his eyes off his brother as he continues to languidly pump his phantasmal member, his pants getting more and more frustrated since he seems to be having trouble reaching orgasm.

Having seen enough, Sans silently walked across the small room and leaned on the bed with a huge grin, "Need a hand with that, Papyrus?"

A loud "NYEH!" rings across the room as the larger skeleton's eyes shoot wide open in surprise. "S-S-Sans, I-I didn't hear you come home! I was just—uhh—um—!"

"Heh. No worries, bro. Here, lemme help with that bone-r."

Papyrus' mouth opens wide to groan at the horrible joke, but all that leaves his mouth is a weak whine at the feeling of Sans' cold hand squeezing at his leaking dick. Skeleton fingers rub over the tip to slick them up with the natural lubrication before tightening the fist and sliding it up and down. Sans is rather impressed with Papyrus' magic. In contrary to his own dick, his brother's lacks girth, but makes up for it in length.

"Damn, Papyrus... Didn't think you knew how to do this."

Only whimpering in return at the teasing comment, Papyrus grabs his pillow and shoves his face into it. Sans immediately reaches up and pulls the pillow away, "No need to hide that cute face. C'mon... Just let go."

There is a burst of blue as one of Sans' eyes goes black while the other lights up. A thick, blue tongue slithers out and wraps around the quivering member, applying the right amount of pressure at the back of the tip where Sans knew would be sensitive, to which Papyrus responds with a strong jerk of his hips.

"S-Saaaaans...!" Papyrus moans needily. "W-We can't—we sh-shouldn't be—aaahn...!"

However in contrary to his words, Papyrus' hands comes up from his side and shakily grip at the skull between his legs. Sans doesn't fight the pressure and opens his mouth wide enough to take in most of his brother's length. He can't take it all since the tip is already hitting the back of his throat, but it doesn't matter. Sans wraps his tongue around the throbbing dick and pumps the rest of the length with his fingers, and within seconds, he hears Papyrus cry out.

Burst after burst of hot, sticky liquid pours out into his mouth, which he gladly swallows. Papyrus obviously has a look of horror at seeing his brother swallow his cum, though Sans can see that there is a part of him enjoying the sight. Feeling one last shiver come from Papyrus' body, Sans finally lets go. "There. Not so hard, eh?" he says while licking off the excess that dribbled down his chin.

A stronger blush appears on Papyrus' cheeks as the orange hue in his eye disappears, his limp member disappearing as well. "Th-That... was actually pretty nice. Thank you, Sans," Papyrus mumbles out with a small smile.

"No prob, bro." Sans stands back up from the bed and is about to leave the room, when two arms suddenly scoop him up. "P-Papyrus?" The smaller skeleton is plopped down back on the bed in between Papyrus' legs, but with his back to his brother's chest. Sans can't see his brother's expression, except for longer skeletal fingers being placed on his crotch area.

"Um... I-I would be quite rude if I didn't lend a hand back. The Great Papyrus never leaves anyone hanging!" Papyrus shyly exclaims. "Now bring out yours so that I may properly, uhh... what is the phrase... oh yes, jack you off!"

For a moment, Sans considers warping away out of his brother's room, yet he immediately thinks against it as cold fingers begin rubbing at his ribs. The feeling is too wonderful as he lets his own magic travel down to his crotch, letting a bulge form under his shorts.

Hey, he already got his brother off. Might as well let Papyrus return the favor if he's willing to do so.

A large grin forms on Sans face as he feels Papyrus' fingers wrap around his thick cock, pumping it in a similar way that he had done so a few moments ago. His brother is a quick learner indeed.


	3. The Black Void (NSFW)

**Summary for the Chapter:**

> I couldn't help but write a Sanster merged with fontcest chapter. Incoming black goo, and slightly inspired by a short comic I saw on tumblr about Gaster and Sans. I'm sorry, I enjoy putting Sans through angst too much!

Sleeping tended to be a frightening experience for Sans. Each night, he would go to his brother for some intimate times before he would be able to allow himself to fall into the deep embrace of slumber. His fear of sleep was rooted to the nightmares that he would experience in them; sometimes the dreams feeling so real that Sans would wake up in a start and wonder if it truly had been a nightmare, or a memory from a past reset.

That was why when Sans felt something cool, gently snaking up his body, he gladly accepted it. The touch felt good—comforting even—as it traveled up from his legs to his spine, coiling around each vertebrae before slithering farther up to his ribs. Whether this wonderful sensation was a dream or not, Sans did not know. Still, that didn't stop him from mumbling sleepily, "Mmm... So nice..."

His words seemed to have had an effect on whatever it was that was making him feel good. The wet and cool feeling worked up higher, caressing the sternum up to the clavicle and then the scapula, sending a shiver down Sans' spine. There was only one person Sans could think of in his dreary state that would arouse him as such, and thus he lovingly muttered their name, "S-Stop it, Papyrus... I'm tryin' to sleep here..."

Suddenly, the movement stopped. Sans' eyes snapped wide open as he felt his body being tugged up and a black mass forced itself through lightly closed jaws. A sense of panic rushed through the small skeleton since all he could see was black; not even the faint outline of his room coming into sight. And then, there was a voice.

A voice that Sans remembers all too well, echoing through his head, though the sound that reverberated in the room was filled with static.

[THAT IS NOT MY NAME, SANS.]

Sans tried to gasp, attempting desperately to apologize, yet the figure in the darkness would have none of this. A familiar, distorted face appeared in the darkness before Sans as more tendrils of shadows slithered in and out of the small body, filling him until Sans gasped out in a tone that wasn't only pain.

"G—Gas—ter—!" Sans managed to gasp out.

[YES.]

The shattered voice—Gaster—answered in a pleased manner.

Though his vision may be blurred from being filled and overtaken by another being, tears welled up in Sans' eyes as he tried to reach towards the figure. More tendrils appeared to pin those arms down, but the ones that had been keeping his mouth pull out, allowing Sans to whimper out.

"Gaster...! Gaster, I've missed you...! I-I still can't find a way—I can't—"

[IN DUE TIME, MY LOVE. IN DUE TIME.]

Those words were all that Sans needed to hear. More muffled cries echoed from between clenched teeth as Gaster continues to fill him until there is no knowing where Gaster begins and the darkness ends.

Sans had missed his lover for far too long. Too many resets and too many timelines traversed that the skeleton was beginning to lose memory of the W.D. Gaster whom he had known for so many years. Papyrus had filled the void that had formed when Gaster was shattered across all time and space, but it hadn't been enough. As much as his love for his brother was strong, his yearning for his lover was powerful as well. Even though this meeting was fleeting, Sans allowed himself to enjoy every moment it.

Unfortunately, that had been his mistake.

[I WAIT. I WATCH. AT TIMES, I WISH YOU WOULD MOVE ON, SANS.]

"No, I-I can't do that, Gaster! You're the last key! Unless I find a way to save you... there's no point to this!"

[PERHAPS. PERHAPS NOT.]

"No..." Sans muttered at the despair ringing in the tone of Gaster's words. "No, no, no...! I am not giving up on you!"

There was no answer, making Sans panic. He knew that Gaster could not exist in one timeline for too long—that his existence was fleeting every second. "Gaster—I need you. I love you! You're the only reason why I still try...!"

[IS THAT SO?]

With those words, the ebon tendrils melted away and his room emerged again. Sans could still sense Gaster behind him in the darkness, but such feelings were lost at the sight before him.

His bedroom door was open. A stunned, trembling, and teary eyed skeleton stood at the doorway.

Papyrus.

His brother.

His other love.

Sans could only watch as Papyrus ran back to his room, slamming the door behind him. A quiet, broken sob fell from Sans' forced smile as he felt Gaster slip away as well.

Papyrus had heard the words he had plead to Gaster. Even though his brother had known about he and Gaster's relationship in the past, such memories were long lost ever since the accident at the Core. His brother, his only other reason for not giving up, had heard him plead his love for another being that Papyrus did not know of anymore.

Only Sans was left in the small room, truly alone for the first time in many timelines as his sobs were drowned in the darkness of his own room.

  

Hence why when the world reset a few days later and Papyrus greeted him with a smile again, Sans couldn't have been more thankful of his accursed gift.


	4. In Each Other's Arms

**Summary for the Chapter:**

> Just some old fashioned, cute cuddles!

Of all the monsters in the underworld, the two skeleton monsters, Papyrus and Sans, were the only two that seemed to not be affected by the cold. Then again, Sans always was seen wearing his blue jacket and Papyrus was relatively well covered with armor and extra cloth, making it hard to tell whether they truly felt no cold or not. Whatever the townspeople of Snowdin might think, that did not mean the brothers wouldn't enjoy burrowing under layers of blankets on days that were especially frigid.

Tonight happened to be one of those nights. Papyrus had been sketching out ideas for new puzzles and traps to capture humans with and had hit a rut. A few ideas still seemed plausible, but overall, he seemed uninspired. With a huff, Papyrus put down his pen and paper; it was best to sleep and revisit the plans in the morning when inspiration didn't come to him, after all.

A few shuffles later of taking off his usual armor and only wearing his black shirt and pants, the tall skeleton dove into his usual race car bed. He burrowed himself under the thick blanket and was about to turn the lights off with his magic when there was a knock at his door.

"Sans?" Papyrus asked, considering that there was only other monster in this house. Lo and behold, his deduction proved true as his brother Sans pokes his head through the door. "What's the matter?"

"Uhh..." Sans mumbled, shuffling his feet on the floor. He doesn't fully come through the door until he sheepishly spoke up, "Hey, so... Would you mind if I... slept in your bed tonight? I'm chilled to the bones after coming back from Grillby's and all."

Seeing his brother shyly asking so was quite adorable in Papyrus' eyes. "Of course! The Great Papyrus never turns down his brother in need of some cuddles!" he happily exclaimed. Papyrus scooched over on his bed as Sans rushed in with a big smile and dove under the blankets. Once Sans popped his head out next to him, Papyrus turned the bedroom lights off.

As soon as Papyrus layed back down, Sans smushed his face into Papyrus' chest and wrapped his short arms around the larger skeleton's body before sighing in content. Papyrus can't stifle the smile at seeing his brother latch onto him. He himself adjusts his arms around the smaller skeleton's frame and nuzzles his jaw onto the smaller skull.

Though neither he or Sans had no body temperature, the sentiment was what mattered.

"G'nite, Pap," Sans mumbled while nuzzling further in.

"Good night, dear brother," Papyrus said back, closing his eyes as well.

The wind was howling outside and the sound of snow hitting the window was loud, but it mattered little to the two in bed. Both of them were safe, and nothing else mattered at that moment.


	5. Voyeuristic Tendencies (NSFW)

**Summary for the Chapter:**

> This is based on a dream I had a couple mornings ago about Sans and Papyrus getting dirty in the back alley of some shady looking place. Time for some possessive, slightly OOC dom Pap and sub Sans with a hint of Grillby.

Everything seemed to be in order when the day began for Sans. He had his usual, daily banter with his brother Papyrus before heading out to work, no human showed up at his sentry post, some water sausage hot dogs were sold at his other job, and then he spent most of his time lounging at Grillby's.

Yes, he had been flirting with the flaming hot proprietor of Grillby's—no pun intended—over his bottle of ketchup, but it was only playful. Even Grillby knew there was nothing behind it as he played along to humor the small skeleton. Once all the customers had gone home, leaving Grillby and Sans left in the quiet restaurant, things did get a little out of hand as Sans decided to tease the bartender further by leaning in closer than usual, almost in a mock kiss when the sound of the bar's entrance opening reached his ears.

Sans wondered for a moment why Grillby quickly stepped back, until a small yelp left his mouth from being yanked off the bar stool. He panicked wondering who was carrying him away in such an undignified manner, only to feel relieved finding out that said carrier was none other than his brother. Sans attempted to give a light-hearted joke with Papyrus... which turned out to be a mistake.

A BIG mistake.

The sound of Papyrus giving an irritated growl shut up Sans in an instant. He was then quickly put back on his feet, somewhere that seemed to look like the back alley behind Grillby's.

"U-Uh... bro?" Sans asked with a worried smile, though that smile quickly disappeared and morphed into panic as he felt Papyrus turn him around and push him towards the brick wall. Both of Sans' hands instinctively shot out to brace himself against the hard, cold wall. Before he had any time to ask what was going on, those words were lost in his mouth.

Papyrus had tugged his pants down to his ankles.

There were no time for questions since Sans immediately felt Papyrus' hands all over his body at once. Sans bit back the loud moan that threatened to come out, all the while gloved hands roughly brushed over his thorax to the sternum, eventually gripping his arched spine and even the quivering pelvis. Just those sensations alone would've been enough to push the smaller skeleton towards his first peak, the only thing keeping him from letting loose being the fact that they were outside, but a sense of dread filled him when Papyrus growled near his ear.

"...What do you think you were doing, Sans?"

"N-Not sure what you mean, bro—nnh!?"

The end of Sans' sentence was cut off by the sharp pain of teeth roughly biting his clavicle from behind. "Don't play coy with me. I saw you getting rather... close with Grillby," Papyrus emphasized his irritation with further bites, the scratches being left behind causing Sans to cry out louder than he would've liked to. "I don't know what games you're playing, but I don't like it." Another bite. "Sans, you're my brother." And another. "You're mine, and mine only!"

A small gasp falls from chattering teeth as the smaller skeleton being pinned against the wall feels something awfully familiar between against his sacrum. "P-Pap, n-not out here...! W-We can't—"

Once again, Sans was cut off as Papyrus positioned himself and slammed his orange glowing member through his brother's pelvis, scraping against all the sensitive bones located there. A burst of blue joins the orange lighting up the dark alley and Sans' nether regions formed as well. Not only does his thick, blue cock springs to formation, what could only be described as either a human vagina or anus also manifested to squeeze down on the orange member.

Sans felt his eyes roll back at the forceful pounding brought on by his brother. He could no longer hold back his moans at the long member thrusting hard into him either, the only thing that mattered to him being his brother's sole attention on him.

"O-Oh, f-fuck! Pa—aah—Papyrus...! Fuck...!"

"That's right, Sans...! Nngh, I'm the one fucking you... N-Now, say who you are!"

Sans braced both hands on the wall, his hips canted towards Papyrus who was furiously bucking into him. His mind was racing a thousand miles a second as he desperately tried to think of what to say back, the pleasure blurring all logical thought processes.

The taller skeleton took that opportunity to lean closer to his bent over brother and mumbled to him what it was that he wished to hear. There was a look of surprise and hesitation in Sans' eyes at those words, yet as his brother resumed to pulling out his dick to tease the tight entrance before thrusting hard back in was all it took for Sans to break.

Neither of them noticed the backdoor opening and a certain bartender walking out as Sans whimpered out, "I-I'm your dirty brother fucker! Y-Your slutty b-brother who needs you to——Aah, p-please, just f-fuck me!"

Papyrus answered such desperate pleas with equally enthusiastic thrusts. "Oh yes! Nngh, that's right! Y-You're MY dirty, slutty, brother fucker...!"  
Slick noises of the long member slipping in and out of the dripping wet orifice, mixed with the groans and moans of the two skeleton monsters echoed through the back alley. Papyrus continued feeding filthy comments to his completely undone brother with each thrust—each comment pushing the both of them closer to completion.

"O-Oh FUCK! P-P-Pap, I-I'm gonna—I'm...!"

Sans' desperate plea roused an even stronger feeling of dominance in the taller skeleton, causing him to grip his brother's pelvis.

"Y-Yes, Sans!"

Thrust.

"Say it...! S-Say that you're going to cum for your brother!"

A stronger thrust.

"C-Cum for me, my perfect, nnh, a-and, my only brother...!"

One final thrust, as Sans screamed his peak. Skeletal fingers scratched the brick wall, leaving deep grooves as the smaller skeleton's body convulsed, his back arching as thick blue liquid spurt out from his engorged member's tip. Orgasm hit Papyrus as well with that last thrust, contrasting orange liquid marking Sans' bones and the wall, along with the blue already on it. Both slumped down to their knees while the phantasmal members disappeared, the two skeletal monsters a panting, completely spent mess on the snow covered ground.

It was only then that the unexpected viewer dicided it was about time for him to make his presence known, and cleared his throat. "...Thank you for that nice show, but you two better clean that up before you leave."

Sans' head shot up at that comment and his face turned a bright blue, seeing that Grillby was standing there with his arms crossed. He could also sense Papyrus glaring up at the flame monster, the tightening of arms around his body being the obvious indicator of his brother's jealousy.

Sans shook his head and gave a small chuckle all the while telling Grillby that they'll make sure to clean up after themselves. As he watched the bartender return a smirk and leave, Sans couldn't help but feel a shiver down his spine at the fact that someone else had watched him beg wantonly for his brother. That shiver transformed quickly into a warmth in his nether regions, his magic almost bursting back to life from that sensation.

(—Oh, I'm hopeless,) Sans thought to himself as he felt another strong urge return to him. "...Hey, bro?"

"Mm...?"

"...Wanna take this back to our place? I don't think I've learned my lesson enough yet."

A small snicker left Sans' mouth at the piercing glare he felt coming from Papyrus. It was rare to see Papyrus get this possessive of him, so might as well enjoy this as long as Sans could milk it.


End file.
